An alibi can be one of the most effective defense strategies if you are wrongly accused of a crime. You will base your defense upon it being impossible for you to have committed the crime because you were somewhere else at the time.
You will of course need proof to back up your claim that you were not at the crime scene as the police believe. There are several ways of doing this:
A person
You need someone to say you were with them. Or that they saw you in a particular place that was not the crime scene at or around the time of the crime.
This could range from your partner telling the police you were home with them, to a dog walker confirming they passed you in the park to your local bartender confirming you were sitting at their bar. If you were genuinely somewhere else, think about who might have seen you.
A receipt
Did you buy anything that could help show you were not at the crime scene? Did you fill up with gas 200 miles away an hour before the crime was committed, for instance? You don’t necessarily need a physical receipt. If you paid by card a statement could confirm the transaction.
Your phone or computer
Did you make any calls around the time of the crime you did not commit? If so, your phone company may be able to help you prove where the call was made from. Similar could apply if you were using the internet on your phone or a computer as browsers sometimes track location.
Showing browser activity could also help. For example, if you were heavily involved in a game of Fortnite, or adding items to your cart on Amazon it could help show you were not committing a crime.
The prosecution may, of course, challenge your alibis. Getting legal help to present them is therefore wise.